Evolutionary Causes and Consequences of Stress-Induced Hypermutation

This presentation was given at the 1st Graduate Students' Conference in Genetics, Genomics and Evolution at the Ben-Gurion University of the Negev, Be'er-Sheva, Israel, September 23, 2012. Abstract: Numerous empirical studies show that stress of various kinds induces a state of hypermutation in bacteria via multiple mechanisms, but theoretical treatment of this intriguing phenomenon is lacking. We used deterministic and stochastic models to study the evolution of stress-induced hypermutation in finite and infinite size populations of bacteria undergoing selection, mutation, recombination, and random genetic drift in constant environments and in changing ones. Our results suggest that stress-induced mutagenesis is advantageous for bacteria at both the individual and the population levels and that it is likely to evolve in natural populations in a wide range of conditions because it is favored by selection. These results imply that mutations are not, as the current view holds, uniformly distributed in populations, but rather that mutations are more common in stressed individuals and populations. This has a significant impact on a various aspects of evolution, genetics, and biology.